[austechwriter] Re: RESOLUTION

Peter,
 
I totally agree with your summary. I have had this discussion with my son (a 
DTP guru) who uses a Mac for the DTP work and a PC to run the business.
 
It's all matter of software.
 
Dennis
Peter Sanders <psanders@xxxxxxxxxxxxxxxx> wrote:
Hi Bill and others

At 06:26 PM 14-07-03 +0800, you wrote:

>Michael, With your intimate knowledge of the MS-DOS ideas on
>resolution, maybe you'd care to illuminate the assembled crowd as to
>why Macintosh systems are used in preference by those who need high
>Res ( and even those who don't). I believe it was yourself that
>provided an erudite explanation of the technical reasons. If it
>wasn't, apologies to the REAL author. Anyway, I am not likely to
>stop using a (now dated) MAC Book G3/400 anytime soon.

The resolution "question" is a function of the monitor in use. It is 
completely irrelevant to the PC or MAC computer. The maximum or highest 
resolution available is ALWAYS limited to the _shadow mask_ within the 
monitor. This shadow mask is a perforated metal screen that effectively 
creates the dots that we see on the glass screen. The shadow mask or mask 
by which it is usually referred, interrupts the electron beam that is 
deflected horizontally and vertically over the phosphor on the inside of 
the glass.

Without this mask all that we would see is a series of horizontal lines 
joined by a fine diagonal line that joins the end of the previous line to 
the beginning of the next line. What this would look like would be almost a 
completely "white" screen. The beam also has to be turned off and on 
depending on whether the dot is to be illuminated or not. This on/off 
timing must also remain coincident with the mask, imagine if the dots were 
on when the beam was _behind_ the mask - no dots!. (All in all, today's 
quality monitor is an amazing piece of technology that we all take for granted)

So to return to the mask, the perforations control the number of visible 
dots and is the reference to which monitors are specified. Therefore a 
monitor of 1024 x 768 has a mask with this number of perforations 1024 
across by 768 down. In ALL instances, the "best" performance from any given 
monitor will be achieved at the mask resolution, ie 1024 x 768 in this 
instance.

This applies in a similar way to the LCD monitor. The LCD will ALWAYS look 
sharper at its maximum resolution as each dot is illuminated correctly, 
different resolutions are not necessarily coincident with the dot pitch 
therefore the LCD has to interpolate (guesstimate) whether a dot should be 
on or off and what colour the dot should be. Subsequently we see some 
characters that are thicker or thinner than others.

To compound the monitor resolution quality, it must be realised that the 
creation of colour images requires three colour "guns" (electron guns fire 
the electron beam against the rear of the glass to excite the phosphor 
coating and make it glow so that we can see the "image"). So the use of the 
mask at ANY given resolution requires EACH of these three electron beams be 
(timed with and ) aligned to operate with the mask. This alignment 
deflection is performed by magnetism, using electromagnetic coils at the 
rear of the picture tube.

As you can probably appreciate, these three "guns" cannot physically be 
located in exactly the same position at the rear of the picture tube, so 
there is already some ever so slight "misalignment" this has to be catered 
for within the electronics that control the beam deflection. Each of these 
three "guns" have to align at the same mask perforation to create the 
colour we see. Misalignment of the beam to the perforation can produce 
fuzzy or incorrectly coloured dots on the screen.

This is all further complicated by the need of the mask to be contoured in 
such a way that it aligns to the inside shape of the glass. For a quality 
image the distance from the mask to the glass must be precisely set across 
the whole area of the screen. Yet another variable is the actual length of 
the beam. The beam needs to be focused at the phosphor. The length of the 
beam from the gun to the centre of the screen is shorter than the length of 
the beam at maximum defection at any perimeter of the screen especially at 
the corners. Consequently the beam becomes slightly out of focus. (This is 
why the screens of monitors and tvs are/were curved, to attempt to keep the 
beam the same length and therefore in focus. LCD displays don't have this 
problem)

For a quality display all of these aspects of a monitor must be taken into 
account. Perhaps this layman's terms (I hope) message describes how and why 
we see fuzzy monitors and sharp monitors.

The only way to have a monitor thoroughly independent of such mask 
resolution is to use a vector type monitor. The resolution of such a 
monitor is a function of the size of the electron beam. Everything drawn on 
a VECTOR monitor is "drawn" by the beam, so to display the letter "M" the 
bean has to be deflected in such a way as to physically follow the contours 
of the letter M. Simple enough for one large letter M on the screen, 
however to do this for even 132 x 40 characters on the screen without even 
contemplating the use of different colours would price such a monitor 
beyond the cheque book of even the largest businesses. To create colour 
filled areas is another difficult task for vector monitors - after all they 
only draw vectors. The phosphor coating on vector monitors is formulated 
for a slow decay so that the vector beam has enough time to complete its 
vector task(s) and return to update previously drawn (and decaying, ie 
fading) vectors.

To my knowledge there is no such monitor available for use as a "normal" pc 
(or MAC) monitor.

To circumvent all of the above, MAC's are used in preference to PCs because 
MACs were the first to do DTP. Therefore more DTP people were drawn (excuse 
the pun) to the MAC, therefore more manufacturers catered for the MAC by 
producing bigger and better (read higher resolution = finer mask) monitors. 
The PC could produce equal output on any given monitor if the video 
hardware and software drivers were available.

The initial analogy could be reviewed in reverse by asking the question 
"Why are pcs used in preference by those who need business applications"? 
The first DTP question "kind of" answers the second and vice-versa. The MAC 
is _perceived_ to be the DTP system, and the PC is perceived to be the 
business computer. Each can be equally as good at the other task if the 
equivalent software/hardware is available and the user demand is 
present. We as computer users have grown used to this demarcation, and 
there is an "us versus them" taunting from time to time, however I think we 
all realise it is all relative to the tools we use for the tasks we perform.

My 0.02c worth (well ok maybe a dollars worth :-{) )

Regards

Peter




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Dennis Frankel

Help Systems Development

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